The instant invention relates to inserts for flexible packages. It relates, more particularly to package inserts adapted to define the shapes of -- and impart rigidity to -- flexible, collapsible bags.
Collapsible bags of thin membraneous materials, chiefly plastics, are extensively employed for packaging purposes in diverse fields. Such packages are economical, readily stored in small volumes, generally transparent so as to permit inspection of the contents, may be imprinted with informative and advertising messages, and in general extremely desirable for many retail applications, particularly in the field of food packaging.
The greatest difficulty in the use of such flexible bags stems from their inherent lack of compressive strength; they do not readily maintain any given shape and tend to deform into the most efficient structural form, most commonly a sphere, adapted to their dimensions and the nature of their contents. As a consequence, such packages cannot be readily applied to granular materials -- flour, sugar, grain kernels and the like -- unless a lumpy appearance is compatible with the ultimate use. Thin-walled bags are also inherently inapplicable to contents with sharp edges and rigid in nature, due to the danger of puncturing the bag material.
Many forms of rigid and semi-rigid inserts have been proposed in the art: mainly to impart a definite outline to the composite package; to protect the package from puncture; to allow the bases of such packages to accept loads without tearing; and to permit stacking of filled packages. None of the proposed inserts are readily adapted to general use -- since they are formed for specific purposes and to support defined shapes -- and most make use of three-dimensional insert structures which must have at least one seam pre-glued or stapled.
It is, therefore, a primary object of the invention to teach the construction and use of inserts capable of securing a rigid shape for flexible package bags, which do not require any joining operations prior to use, and which may be stored in the form of flat blanks or pre-folded shapes and assembled at the point of use.
It is a further object of the invention to provide an insert which may be readily expanded manually, or automatically, in a flexible bag which forms the external sheath of the package with the insert and which, upon such expansion, forms a reinforced seam at the confluence of the free edges in the initial blank.
It is also an object of the invention to provide blanks for the forming of package inserts which are slit and formed at their free edges to define alternating straight and bent tabs in a crenellated structure readily interleaved into a self-supporting seam.